The need for effective herbicides needs no special emphasis. The control of weeds and undesirable vegetation is of great economic importance since weed competition inhibits the production of foliage, fruit or seed of agricultural crops. The presence of weeds can reduce harvesting efficiency and the quality of the harvested crop. Weeds on non-cropped areas may cause a fire hazard, undesirable drifting of sand or snow, and/or irritation to persons with allergies. Thus, suppression of undesirable weed growth is very advantageous.
Accordingly, it is an object of this invention to provide effective novel herbicidal compounds, as well as to provide novel herbicidal compositions and novel methods of controlling weeds.
Various heterocyclic compounds useful as herbicides have been described in U.S. Pat. Nos. 5,451,566, 5,444,038 and 5,369,086 which are all incorporated herein by reference. For instance, U.S. Pat. No. 5,451,566 describes 1-aryl pyrrolopyridine compounds useful as herbicidal agents. In addition, U.S. Pat. No. 5,444,038 describes 1-arylindazole compounds which are useful as herbicides. Similarly, U.S. Pat. No. 5,369,086 describes 1-aryl-N-benzotriazoles. None of the aforementioned patents disclose a compound wherein the 1-aryl group is a pyridyl N-oxide which possesses herbicidal activity.
Surprisingly, the inventors have found that the heterocyclic pyridyl N-oxide compounds described herein below exhibit unexpectedly desirable herbicidal activity. The compounds have been found to be effective in both preemergent and postemergent application and on a variety of weed species.